Thursday, May 7, 2015

Tuesday, May 5, brought
heavy rainfall to areas throughout Central Texas. While central Texans
typically welcome rain as a much-needed event, the specific locations that
receive the rain impact the Barton Springs segment of the Edwards aquifer
differently. Northern Travis County experienced flash flooding as a result of
the rain with Bull and Walnut Creeks experiencing over 4,000 cubic feet per
second (cfs) according to LCRA flow stations. We can generally say that
significant recharge occurs when Onion Creek (in Southern Travis & Northern
Hays counties) is flowing all the way across the recharge zone to Antioch Cave.
However, Hays County received very little rainfall by comparison. Creeks within
the critical recharge zone like Onion, Slaughter, Bear and Little Bear saw
small increases in flow. For example, flow in Onion Creek (at Driftwood) rose
from 25 cfs to 35 cfs from the rains. Antioch cave, the largest-capacity
recharge feature in Onion Creek near Buda, did not receive any creek flow or
recharge.

The Edwards Aquifer recharge
zone provides direct inlets for recharging the aquifer. When rain falls in the watershed
upstream of this critical area, especially in northern Hays County, streamflow
provides sustained recharge to features like Antioch Cave and other sinkholes, which
act as conduits directly into the aquifer. As a result, the water supply is
bolstered and habitats for critters like the Barton Springs salamander are
maintained.

Although the recharge
was not significant to the aquifer as a whole, all things considered, Tuesday
night’s rain helped keep Barton Springs flowing for Austin’s summer bathers and
provided needed thirst-quenching for local plants and wildlife. The rains also
helped continue the rise in groundwater levels seen in the Lovelady monitor
well. For the year, the Austin areas is 0.3 in above average for rainfall. Less
than a week into May, we’ve received almost a fourth of the month’s historical
rainfall (0.97in of 4.4in) according to the BSEACD station. Let’s hope the
rains continue to visit Central Texas and the Edwards Aquifer recharge zone is
not left out.

The
outlook for future rainfall looks promising as the National Weather Service
Climate Prediction Center anticipates that with the wet start to the month
across the plains, forecasts indicate an active southern stream and a generally
wet pattern for much of the United States.

And
to folks who encounter flash flooding, remember it’s always safer to turn
around at flooded low water crossings!

Drought Rules

Either Barton Springs OR the Lovelady Well can trigger a drought declaration by the Board. However, BOTH Barton Springs AND the Lovelady Well must be above their respective drought trigger levels to exit a drought declaration.